A variety of techniques are employed to consolidate a workpiece so as to form a part having a desired configuration. For example, vacuum hot pressing or hot isostatic pressing may be employed to consolidate a workpiece. Alternatively, workpieces may be consolidated by the application of pressure concurrent with the inductive heating of the workpiece. In this regard, an apparatus for consolidating a workpiece may include first and second dies which cooperate to define an internal cavity. A susceptor may line the internal cavity and, in turn, define a die cavity for receiving the workpiece. The susceptor is formed of a conductive material, while the first and second dies are formed of a material transparent to electromagnetic energy. In order to heat the susceptor and, in turn, the workpiece, an induction heating coil is positioned proximate the first and second dies for generating electromagnetic energy, such as an oscillating electromagnetic field. Since the first and second dies are transparent to the electromagnetic energy, the electromagnetic energy travels through the dies and interacts with the susceptor, thereby rapidly heating the susceptor. Since the workpiece is in thermal contact with the susceptor, the heating of the susceptor also serves to heat the workpiece.
Susceptors may be referred to as smart susceptors because the material composition of the susceptor is specifically chosen to produce a set temperature point when used in an induction processing system. In this regard, the material composition of the susceptor may be chosen such that the Curie point of the susceptor at which there is a transition between the ferromagnetic and paramagnetic phases of the material forming the susceptor is used to set the equilibrium temperature point to which the susceptor is inductively heated.
In order to permit the formation to occur at lower pressures and temperatures, a forming technique has been developed to take advantage of the unique properties of metallic materials when the crystallographic characteristics of the metallic materials are changing. In this regard, a workpiece, such as a preform, can be placed within a die cavity and pressure applied thereto. An induction heating coil can then be energized so as to generate an oscillating electromagnetic field which heats the susceptor and, in turn, the workpiece to a temperature proximate the phase transformation temperature rangeover which one solid phase of the workpiece changes completely to a second solid phase. The temperature of the workpiece is then repeatedly cycled above and below the phase transformation temperature range in order to consolidate the workpiece.
While this technique is effective for consolidating workpieces, it would be advantageous to form the workpiece to have or at least to closely approximate its final desired shape in order to minimize the work required following consolidation to appropriately shape the workpiece. However, it is frequently desirable for a workpiece to have a complex configuration having portions which extend in different directions. In order to appropriately consolidate the workpiece, it is therefore desirable for the die assembly to apply relatively even pressure across all of the surfaces of the workpiece such that the consolidation process proceeds uniformly. In instances in which the desired configuration of the workpiece is complex, however, the die assembly may require double or triple acting dies, each oriented in a different direction so as to appropriately apply pressure to a respective portion of the workpiece. The use of double or triple acting dies increases the complexity of the die assembly as well as the overall cost of the die assembly. Thus, it would be desirable to provide relatively even pressure to the surfaces of a workpiece, including a complexly configured workpiece, in the manner that would not require multiple die presses, but which could instead be formed with a single acting die.